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Dev Biol. 2014 Dec 15;396(2):201-13. doi: 10.1016/j.ydbio.2014.10.002. Epub 2014 Oct 18.

Hepatic Notch2 deficiency leads to bile duct agenesis perinatally and secondary bile duct formation after weaning.

Author information

1
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands; Emma Children's Hospital AMC and Pediatric Surgical Center of Amsterdam, Academic Medical Center, Amsterdam, The Netherlands. Electronic address: f.a.falix@amc.nl.
2
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands; Emma Children's Hospital AMC and Pediatric Surgical Center of Amsterdam, Academic Medical Center, Amsterdam, The Netherlands.
3
Tytgat Institute for Liver and Intestinal Research, Academic Medical Center, Amsterdam, The Netherlands.
4
Université Catholique de Louvain and the Duve Institute, Brussels, Belgium.
5
Emma Children's Hospital AMC and Pediatric Surgical Center of Amsterdam, Academic Medical Center, Amsterdam, The Netherlands.

Abstract

Notch signaling plays an acknowledged role in bile-duct development, but its involvement in cholangiocyte-fate determination remains incompletely understood. We investigated the effects of early Notch2 deletion in Notch2(fl/fl)/Alfp-Cre(tg/-) ("Notch2-cKO") and Notch2(fl/fl)/Alfp-Cre(-/-) ("control") mice. Fetal and neonatal Notch2-cKO livers were devoid of cytokeratin19 (CK19)-, Dolichos-biflorus agglutinin (DBA)-, and SOX9-positive ductal structures, demonstrating absence of prenatal cholangiocyte differentiation. Despite extensive cholestatic hepatocyte necrosis and growth retardation, mortality was only ~15%. Unexpectedly, a slow process of secondary cholangiocyte differentiation and bile-duct formation was initiated around weaning that histologically resembled the ductular reaction. Newly formed ducts varied from rare and non-connected, to multiple, disorganized tubular structures that connected to the extrahepatic bile ducts. Jaundice had disappeared in ~30% of Notch2-cKO mice by 6 months. The absence of NOTCH2 protein in postnatally differentiating cholangiocyte nuclei of Notch2-cKO mice showed that these cells had not originated from non-recombined precursor cells. Notch2 and Hnf6 mRNA levels were permanently decreased in Notch2-cKO livers. Perinatally, Foxa1, Foxa2, Hhex, Hnf1β, Cebpα and Sox9 mRNA levels were all significantly lower in Notch2-cKO than control mice, but all except Foxa2 returned to normal or increased levels after weaning, coincident with the observed secondary bile-duct formation. Interestingly, Hhex and Sox9 mRNA levels remained elevated in icteric 6 months old Notch2-cKOs, but decreased to control levels in non-icteric Notch2-cKOs, implying a key role in secondary bile-duct formation.

CONCLUSION:

Cholangiocyte differentiation becomes progressively less dependent on NOTCH2 signaling with age, suggesting that ductal-plate formation is dependent on NOTCH2, but subsequent cholangiocyte differentiation is not.

KEYWORDS:

Cholangiocytes; Ductal plate; Ductular reaction; Liver; Notch2

PMID:
25446530
DOI:
10.1016/j.ydbio.2014.10.002
[Indexed for MEDLINE]
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